Trunking system of radio distribution



April 13 1926. 1,580,409

E. E. CLEMENT muuxme SYSTEM OF RADIO DISTRIBUTION Filed Feb. 14, 1925 4 Sheets-Sheet 1 i Q Imu- April 13 1926.

E. E. CLEMENT TRUNKING SYSTEM OF RADIO DISTRIBUTION Filed Feb. 14 1925 4 Sheets-Sheet 2 i a Nh m April 13,1926. 1,580,409

E. E. CLEMENT TRUNKING SYSTEM OF RADIO DISTRIBUTION Filed Feb. 14, 1925 4 Sheets-Sheet 4 A w TEJT/IVG 7; B n lP/lfil7t/6 o 76 V F 1 L91) L O x I I i I I 96 I F I a ar/em? Mack/554215 J I omsspmsse is Patented Apr. 13, 1926.

UNITED STATES PATENT OFFICE.

I EDWARD E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR TO EDWARD F. COLLAJDAY, OF WASHINGTON, DISTRICT OF COLUMBIA.

TRUNKING SYSTEM OF RADIO DISTRIBUTION.

Application filed February 14, 1925. Serial No. 9,355.

To all whom it may concern:

Be it known that I, EDWARD E. CLEMENT, a citizen of the United States, residing at \Vashington, in the District of Columbia, have invented certain new and useful Improvements in Trunking Systems of Radio Distribution, of which the following is a specification, reference being had therein to the accompanying drawings.

The present invention is a continuation in part of my copending application Serial No. 754,406, filed December 6. 1921; it re. lates to systems of radio broadcast distribution, and has for its object to organize such a system so that a program may be originated, relayed and distributed over a large area, uniformly and in a systematic and orderly manner to aut-l'iorized users or subscribers who will get the full benefit of the use of vacuum tubes in receiving and amplifying without the necessity of maintaining tubes at their stations, the tubes used by the subscribers in receiving being located at central points where supervision, maintenance power supply and control may be centralized and put under the care of expert operators.

In the prior application above referred to, both relay distribution and supervision of the broadcast service for a group of subscribers is carried on at the central station or exchange local to the group. The object of the present invention ditfers from the aforesaid in that a district relay station and radio studio common to several subscribers central stations, is provided for distributing broadcast matter to the central stations by radio, the central stations distributing the broadcast matter to their respective sunscribers by wire, while supervision of the broadcast service as distributed by the several central stations and received by the subscribers is delegated to one of the central stations, and supervision of the broadcast service as furnished by the district station and received at the several central stations is reserved by the district station.

The invention is applicable to manual automatic or so-called semi-automatic or automanual telephone systems. the principles involved not being changed by dilferent methods of effecting or controlling the neces sary electrical switching connections.

My invention is illustrated in the accompanying drawings, in which:

Figs. 1 and 2 indicate diagrammatically, the telephone exchange portion and the broadcast distributing portion of a subscribers central station forming part of my system.

Fig. 3 is a diagram of the district radio relay station and studio.

Fig. 4 is a diagram of the primary supervisors station at the main central station.

Fig. 5 is a schematic diagram showing the system as applied to a district containing several local or exchange groups.

Referring to the drawing in detail and first to Fig. 1, this shows the essential cir cuits of an ordinary telephone exchange system in which JJ' are line terminal jacks forming the terminals of telephone lines leading to stations to be interconnected such as the subscribers station A. These jacks are arranged to be interconnected through the usual answering and calling plugs P-P' forming the terminals of the usual common battery cord circuit shown. The central office terminals of each line are provided with the usual line relay L, line lamp L and cut-off relay L lVhere service is to be metered a recording meter M is also individually associated with the line. Thus,

the circuit arrangement here shown is that of the standard multiple switchboard, common battery, telephone exchange system, and as such is well understood in the art further detailed description thereof will be here deferred and brought out later in the description of operation. In addition to the usual line terminal, multiples 1, 2 and 3, representing multiples of the tip, sleeve and test or cut-ofi' circuits, respectively, I provide a fourth conductor 4 leading from a contact on the line relay along with the multiple conductors 1, 2 and 3 to the broadcast distributing system diagrammed in Fig. 2.

Fig. 2 shows the broadcast distributing system of which the portion to the left of the dotted line is situated at the central ofiice and connected with the subscribers telephone line terminal apparatus of the telephone central C (Fig. 1) through conductors 1, 2, 3 and 4, while the portion to the right of the dotted line in Fig. 2 is situated at the subscribers substation and connected with the subscribers telephone substation apparatus A (Fig. 1) through the multiple conductors 5 and 6. In Fig. 2 the subscribers line multiples 1-2 terminate in the spring contacts 7-8 of a jack 9 which contacts are arranged upon the insertion of the dummy plug 10 to be spread apart to engage with the stationary contacts 11-12 to extend the connection of the multiples 1-2 to conductors 13-14. The conductor 13 connects with the positive terminal of the common central ofiice battery B through the winding 15 of a repeating coil 19 while the conductor 14 connects with the negative terminal of the battery B through a sleeve or supervisory relay 42 and the winding 16 of a repeating coil 20. An audion tube 37, individual to the line, is also provided which is arranged with its output or plate circuit conductors 21-22 connected in series with the windings 17 and 18 of the repeating coils 19 and 20 and a plate battery B. The input circuit of the tube 37 is arranged to be connected through contacts 23-24 on the supervisory relay 42 and conductors 25-26 to the program busses 27-28 to which are connected the audio output terminals of the radio receiver or broadcast relay and distributer 29 which may be of any known or other suitable type of radio receiver capable of furnishing the busses 27-28 with audio signaling currents of sufficient strength to supply the input circuits of the several subscribers line tubes 37, it being understood that several such line tubes (not shown) are supplied from the common busses as indicated by the multiple branch conductors 30. A normally closed contact 31 on the relay 42 connects the common battery B to the conductor 32 which terminates in a normally open contact 33 in the jack 9 operable to extend the connection of conductor 32 to the signaling conductor 4 to supply battery potential thereto. This signal conductor is arranged to be connected with battery upon energization of the subscribers line relay through the line relay contact 52, Fig. 1. The relay 42, Fig. 2, also controls the connection of the multiple test circuit conductor 3 to the common battery B through a normally open contact 34 which comiection includes a special tone test device of any known or other suitable form, indicated diagrammatically at 35, operable to superpose a characteristic signal current on the test conductor 3. Connected between the signal conductor 4 and ground is a signal lamp 36 mounted near the jack 9 in the manner of the usual telephone line or call lamp.

Certain parts of the circuits of Figs. 1

. and 2 are shown connected to or terminating the description of Figs. 3 and 4 with which they are functionally related. The circuits and apparatus shown in Figs. 1 and 2 are those of the main central station and one of its subscribers stations but it is to be noted that the other central stations served by the common district station are similarly equipped. For a broader and clearer view of the relative arrangement and identity of the different stations reference is to be had to Fig. 5, wherein 38 indicates the district station, 91 the main central station (diagrammed in detail in Figs. 1 and 2), A, A the telephone and broadcast receiving apparatus, respectively, at a subscribers station connected with the central station 91, and 92 and 93 other central stations similar in all respects to station 91 except that the primary supervisor and supervising equipment are not situated thereat. There are other central stations and their subscribers stations being supervised from the main central station 91 over trunk lines.

in Fig. 3, which shows the equipment at the district or relay station, the radio relay apparatus indicated diagrammatically at 39 may be of any known or other suitable form operable to receive radio broadcast matter from one or more distant stations and relay the same to the several subscribers central distributing stations like that of Fig. 2. These district stations are preferably also provided with means for originating broadcast matter, for example, a microphone 40 and modulator 41 connected with the relay apparatus.

A telephone trunk 101-102 connects the district station Fig. 3, with the central station Figs. 1 and 2, which trunk terminates in a jack 38 at the district station, Fig. 3, and in the usual line terminal apparatus 43 at the central station Fig. 1, which line terminal apparatus is the same in all respects as that of the subscriber A. This terminal apparatus, like that of the substation A is provided with multiple conductors 221, 222, 223 and a signaling conductor 224 corresponding in function to the conductors 1, 2, 3 and 4 respectively, of the substation A, leading to broadcast line terminal equipment not shown but similar in all respects to that shown in Fig. 1 associated with the line terminals of the substation A.

Other jacks 44 and 45 at the district station form the terminals of other telephone trunks 201-202 and 301-302 connecting with other central stations like that of Figs. 1 and 2. Any of the lines 101-102, 201- 202, etc. may be connected with the supervisory telephone set 46 through the plug 47 and the respective line jacks 38, 44, etc. Anv of the lines 101-102. etc. may be also operatively connected with the modulator 41 through the plug 48 and their associated line jacks 38, etc. To eflect other combinations of connections between the jacks 38, etc. the modulator 41 and telephone set 46, the said jacks are connected with multiple jacks 138, etc., and connecting cords or link circuits such as 49 provided for connecting one or more lines to either or both the modulator and telephone set.

In addition to the ordinary telephone lines 101-102, etc., the district station is connected with the broadcast distributing portion, (Fig. 2) of the central station through a pair of test circuits comprising a test trunk 150-151 and an order circuit 152- 153. The test trunk is a simple normally disconnected two wire circuit terminating at both ends in simple jacks 50 and 51. The order circuit 152-153 terminates at the dis- .trict station in a jack 7 2 and at the central station in a jack 73 and the usual common battery line terminal apparatus 54 with line lamp 55, the jacks 51, 73 and lamp 54 being located before an operator at the central station equipped with means for communicating with an operator at the district station which means may he an ordinary common battery cord circuit indicated symbolically at 56 (Fig. 2), and means for connecting the test trunk with the broadcast busses 27-28, which latter means is here shown as a simple plug and cord, link circuit 57 for connecting the jack 51 with a jack 58 connected with the busses 27-28. A. the district station, Fig. 3, an operators testing apparatus 59 is arranged to be connected with the test trunk through a plug and the jack 50. Other pairs of test trunks and order circuits 161-162, 163-161, etc. extend from the district station to other central stations equipped like that of Figs. 1 and 2, said trunks and order circuits terminating at the district station in jacks 81, 83, etc. situated with the acks 5'0, 72, before the test opera-tor and accessible to the plug 80. To enable tests to be made of a relay apparatus at the central office with all lines disconnected therefrom but without interrupting the service, the central oiiice may be provided with a duplicate relay apparatus 89 arranged to be connected to the busses 27-28 by closure of a switch 70 when the apparatus 29 is disconnected by opening the switch 71, for test purposes. I

In Fig. 1 are shown the circuits and apparatus used by the primary supervisor or wire chief at the main central station. This equipment hereinafter termed the primary wire chiefs equipment or position is indicated generally in Figs. 1 and 5 by the reference numeral 97. It comprises testing and supervisory apparatus like that of Fig. 3, that is, a telephone listening set 7 1 and a set of testing apparatus 98 both adapted to be connected through their respective plug terminals 99 and 100, respectively, with the jacks 75, 77, 103, etc. forming the terminals of trunks and lines leading to the several different central stations. The jacks 7 5 and 76 form the terminals of a pair of test trunks 78 and 79 leading to the broadcast distributing section of the main central station, Fig. 2, where they terminate in jacks 109 and 110, respectively, situated before an assistant or secondary wire chief with j urisdiction local to the main exchange. Associated with these test trunks 78,79 is a telephone line or order circuit 84 terminating at the wire chiefs position (Fig. 1) in the jacks 77 located adjacent to the jacks 7 5 and 76, and terminating at the main exchange in the usual common battery line terminal apparatus 111, the jacks 112 and calling lamp 113 of which is situated near the jacks 109 and 110 before the secondary wire chief. Other groups of jacks 103 to 105 and 106 to 108 form the terminals of groups of trunks and telephone circuits 11d and 115, similar to the group 78 to 84, leading to the other central stations 92 and 93. (Fig. 5).

At the main central station (Fig. 2) the secondary wire chief is provided with a suitable telephone answering, calling and interconnecting device preferably in the form of an ordinary common battery, operators cord circuit indicated at 87, and other more simple connecting links or dummy cord circuits and 86 for effecting connections between the jacks 109, 110 and 112 and the jacks 88, 91 and 95. The jack 88 is a multiple jack for the subscribers line 09-78, being permanently connected thereto through line multiples 1-2 and conductors 116-117. The jack 94 forms an extension of the input terminals of the subscribers line tube 37 through conductors 118-119, and the jack forms the terminals of an order circuit 120-121, terminating at the telephone operators switchboard (Fig. 1) in a. jack 122 with a calling lamp 123 operatively associated therewith through the usual line terminal apparatus like that indicated at 43 (Fig. 1). Thus by use of the link circuits 85 and 86 and the cord circuit 87, the secondary wire chief at the central station may make various connections between the trunks 78-79 and telephone line 84 and the circuits of the central station in response to instructions received over the line 81 from the primary wire chief.

As the purpose of the order circuit 120- 121 is to enable the secondary wire chief to extend the primary wire chiefs order circuit line 84: to the jack 122 at the telephone operators position, this jack may form the terminal of a line or trunk leading directly from the primary wire chief's position. This would be desirable at least for the main central station because of the chief operators nearness.

\Vhile the circuits and apparatus of the main central station only are here shown in detailed diagram, it is to be understood that those of the other central stations 92 and 93 (Fig. are the same in all respects, each central station having its secondary wire chief, assistant to the primary wire chief.

Before proceeding with the detailed description of operation of the system, a broader conception of the general functional relation of the different station elements of the system may be had by reviewing Fig. 5 wherein it will be noted that the district station 96 is operatively associated with the several groups of subscribers central stations 91, 92 and 93 through both radio and wire channels as indicated by the antenna symbols and connecting lines. The district station 96 is arranged to receive broadcast matter from any distant station and relay the same by radio to the several subscribers central stations as indicated by the arrows adjacent to the antenna symbols on the several stations. The station 91, represents the main central station diagrammed in detail in Figs. 1 and 2, while the subscribers substation AA is the one similarly designated in Figs. 1 and 2.

In operation, broadcast matter is transmitted from the district station (Fig. 3) by radio to the relay apparatus at the difi'erent central stations such as the relay and distributor 29 (Fig. 2), the audio output circuit of which is connected through switch 71 to the busses 2728. A subscriber at substation A desiring broadcast service, now connects his broadcast receiving or extension set A to the line by inserting the receiver plug P in the jack J which connects his receiver 64 across the line multiples 5 and 6 through the booster coil windings 60-65 and condenser 66 in series, and closes a path for direct current between the multiples 5 and 6 through coil 60, lower spring of jack J transmitter 62 and signaling key 63.

This energizes the subscribers line relay at the central oflice in the usual manner by current from the central oflice, common battery B, conductor 68, right hand winding of relay L, line conductor 69, to subscribers substation A, line multiple 5. to subscribers broadcast receiving set A (Fig. 2), coil 60, transmitter 62, contacts of key 63, conductor 6, 70, left hand winding of line relay L and back to battery B. Actuation of the line relay energizes the line lamp L by closure of a local circuit which may be traced from common battery B through circuit elements L 71, 68, and back to battery B. This causes the line lamp L at the telephone operators switchboard to glow, but only for a moment, as the subscriber wanting broadcast service will immediately operate his signal key 63 to rapidly open and close his line circuit which causes his line lamp to flicker instead of glowing steadily and so indicate to the telephone operator (Fig. 1)

that the subscriber is not calling for a telephone connection. This intermittent actuation of the subscribers telephone line relay L also causes a flickering of the lamp 36 (Fig. 2) associated with his broadcast service, multiple jack 9 situated before the broadcast service operator. This operator perceiving the flickering of the lamp interprets the signal as a call for broadcast ser vice and in answer thereto inserts the actuating plug 10 in the jack 9. This effects the closure of contact 711, 812, and 33. Closure of the contacts 7-11, 812, connects the battery B (Fig. 2) across the subscribers line through the repeating coil windings 16 and the sleeve supervisory relay 42 which connection may be traced from battery B (Fig. 2) through circuit elements 15, 13, 11, 7, 1, (into Fig. 1), 69, 5, (into Fig. 2), 60, 62, 6, (into Fig. 1) 70, 2, (into Fig. 2) 8-12, 14:, 42, 16, back to battery B. As this completes the circuit including the battery B and the relay 52, this relay is energized and closes the circuit of the cut-off relay L (Fig. 1), over a path which may be traced from the common battery B (Fig. 2) through the circuit elements 35, 3-1, 3, (into Fig. 1), cut-ofl relay L, 68, and through ground back to common battery B. Energization of the cut-off relay disconnects the subscribers line from the telephone line signal apparatus in the usual manner, thus causing the line lamp L to become deenergized and extinguishing both signal lamps L and 36. As the cut-off relay is held energized over the test conductor 3 by battery supplied thereto through the special tone test device 35, a telephone operator in testing the line will receive this characteristic tone test instead of the usual click in the ear indicating that the subscribers line is busy with the special or broacast service which may or may not be interrupted for telephone service according to the wishes of the subscriber. Euergization of the relay 42 (Fig. 2) also connects the input circuit of the subscribers line tube 37 to the broadcast busses 27-28 by way of contacts 23, 2 1 and conductors 25, 26, respectively. The actuation of relay 42 also energizes the sub scribers line lamp 37 by closure of its filament circuits through contact 351, and filament battery F. The plate circuitof the tube 37 is energized from battery B through the plate circuit conductors 21, 22. and repeating coil windings 17 and 18. Thus the broadcast matter supplied to the input circuit of the tube 37 from the busses 27-28 is amplified in the output circuit 22, 18, B 17, 21, and transferred into the subscribers line circuit by the repeating coil windings 15-16 included in the line circuit. The broadcast signal currents passing through the winding of the booster coil 61 are repeated in the coil 65 and included in circuit with the subscribers broadcast telephone receiver 64 which circuit may be traced from the coil 65 through circuit elements J P 64, P, J 89, 62, 63, 266, back to coil 65.

When the subscriber desires to discontinue the use of the broadcast service, the plug P (Fig. 2) is pulled which opens the line circuit at the jack 9 deenergizing the relay 42, which in turn connects the battery to the signal circuit conductor 4 through relay contact 31 and energizes the radio service signal lamp 36 over a circuit which may be traced from common battery B through circuit elements 31, 32, 33, 4, 36 to ground and back to common battery B. This causes the lamp 36 to glow steadily indicating to the broadcast service operator that a disconnection is desired whereupon the operator pulls the plug 10 which opens all the contacts of jack 9 and restores the circuits to normal.

When it is desired to originate broadcast matter at the district station (Fig. ,3), microphone 40 is used which operates through a modulator and transmitting portion of the radio relay 39, the circuits and apparatus of which modulator and transmitting portion of the relay being of any known or other suitable type. Where it is desired to permit a subscriber to broadcast from his substation he may be connected through the ordinary telephone exchange circuit (Fig. 1) to the telephone line circuit 101-102 terminating in the multiple jacks 38 and 138 at the district station (Fig. 3) from which the connection may be extended by plug 48 to the modulator of the relay transmitter 39. To enable the operator at the district station to listen in on the broadcasting subscribers line, the listening set 46 may be connected to the line through the plug 47 and the remaining one of the multiple jacks 38 and 138.

A test of the quality of reception at the central station (Fig. 2) may be had from the district station (Fig. 3) over the testing trunk 150-151 through the jack and the plug connection 50 and 47, and the listening set 46, the testing trunk having been connected with the output of the receiver 29 (Fig. 2) through jacks 51 and 72, and the line circuit 57. If it is desired that this test he made on the output of the receiver 29 free of all subscribers line connections, a duplicate relay transmitting apparatus 89 may be put into service and connected to the distributing busses by closure of swltch 7 0 before opening the switch 71 to clear the apparatus 29, thus preventing interruption of the broadcast service.

All tests of all subscribers circuits and central ofiice circuits that have to do with the subscribers reception of the broadcast matter furnished at the central stations, are made by the primary wire chief from the wire chiefs position 97 (Figs. 4 and 5), preferably located at the main central station, although it is to be understood that it may be at or near any one of the central stations or at a special station.

In making these tests the primary wire chief makes use of his telephone set 74 to communicate his wants over one of the order circuits 84, etc. to the secondary wire chief at the particular central station whose circuits he desires to test, which testing, if in the nature of supervision of the quality of reception by the subscriber, may be made by the use of the telephone set 74, and if made for determining various conditions of the circuits, the testing apparatus 98 is used which may comprise any known or other suitable arrangement of testing apparatus and circuits such as a source of current, ammeter, voltmeter, etc.

For example, should the primary wire chief desire to test the conductor and opera tion of the subscribers line tube 37 (Fig. 2) independently of its connection with the dis tributing busses 2728, he should connect his telephone set 74 with the order circuit 84 through the plug and jack 99-77 and call the secondary wire chief at the central station through signal lamp 113 in the usual manner of making a telephone call, whereupon the secondary wire chief would establish connection through the answering plug of the cord circuit apparatus 87 and jack 112. The primary wire chief would then order a connection between the trunk 7 8 and jack 88, and trunk 79 and jack 94 through the link circuits 85 and 86 respectively, and instruct the local wire chief to open the switch 124. The primary wire chief would then connect his testing apparatus 98 with the input circuit of the subscribers line tube 37, through plug and jack 10076, trunk 79, (into Fig. 2) plug and jack connections 1108694, and extension conductors 118- 119, and connect his telephone set 74 through plug and jack connection 99-75, trunk 78, (into Fig. 2) plug and jack connections 1098588, and extension conductors 116- 117 to the subscribers line multiples 12 which connect with the output circuit of the subscribers tube set through the connections of jack 9. The wire chief at the position 97 would then be able to supply the input circuit of the subscribers tube with various forms of current and detect the resultant effects on the line multiples 12 through his telephone set 74 or other apparatus accord ing to the nature of the test.

While, for the sake of simplicity of disclosure, I have illustrated and described the use of but a single broadcast relay apparatus at the central exchanges, it is of course obvious that these elements may be multiplied to afford the subscribers a choice of one of several concurrent programs as shown mam and described in my copcnding application, Serial No. 3,861, filed January 21, 1925.

Vhile I have herein described and illus trated the use of audio frequencies for distribution to the subscribers over their wired circuits the invention is not limited to such frequencies, but may employ also superaudio frequencies, so long as they are suitable for line transmission. I11 the work hereinbefore done by Major General Squicr and others, frequencies ranging from 25 to 100 kilocycles per second have been found suitable for this purpose. In order to make such frequencies available for distribution among the subscribers in the present system, the connections from the central station receiving and relaying distributing apparatus remain practically the same, as that described and shown in Fig. 2, the input or grid circuit of the individual line tube 37 also remaining the same. The repeating coil connection to each line must either be supplemented or replaced however by a filter connection, preferably permanent, which will permit super-audio frequency currents to be transmitted from the plate circuit of the tube to and over the line circuit to the subscribers station, while the battery current from the battery B will simultaneously flow over the subscribers line for signaling and talking purposes of the subscriber. At the subscribers station, complementary connections must be made, and a detector radio set must be connected to receive superaudio currents over the line, while the telephone elements are connected, preferably in parallel, to receive the battery current and transmit and receive audio frequency waves. Such an arrangement is shown as to its principles in Letters Patent granted me January 6, 1925, No. 1,552,362, to which reference is had for further explanation of the principles involved.

I do not claim broadly herein a district station and local distributing stations as such, nor amplifiers associated with the individual lines, these being claimed in my prior copending applications, Serial No. 746,357, filed October 28, 1924; and Serial No. 754,406, filed December 6, 1924.

What I claim is:

1. In a system of radio broadcast distribution, a district broadcast service station, a plurality of central stations each with subscribers substations and wire lines interconnecting them, radio broadcast transmitting means at the district station, distributing relay means at each central station for relaying the matter broadcasted from the district station onto the subscribers wire lines at a frequency suitable for line transmission, and means for supervising and testing the circults and apparatus of all said central stations and their subscribers stations from a common point.

2. In a system of radio broadcast distribution, a district broadcast service station. a plurality of central stations each with subscribers substations and wire lines interconnecting them, radio broadcast transmitting means at the district station, distributing relay means at each central station for relaying the matter broadcasted from the district station onto distributing busses at a frequency suitable for line transmission, subscribers relay means at the central station individual to each subscriber-s line for connecting the line with the busses, and means for supervising the operation of the said relay means at the different stations from a common point.

3. In a system of radio broadcast distribution, a district broadcast service station, a plurality of central stations each with subscribers substations and wire lines interconnecting them, radio broadcast transmitting means at the district station, distributing relay means at each central station for relaying the matter broadcasted from the district station onto distributing busses at a frequency suitable for line transmission, subscribers' relay means at the central station for individually connecting a subscribers line with the busses, radio wire chiefs supervisory and testing circuits extending between the district station and the central stations with switching means at the central stations for connecting said circuits with the distributing relay means, wire chiefs supervisory and testing circuits extending from a common point to switching points in said central stations, and means at the switching points for connecting the Wire chiefs circuit to different parts of the different subscribers relay means.

4. In a system of radio broadcast distribution, a district broadcast service station, a plurality of central stations having radio receiving means, a plurality of subscribers served by each central station through receiving means individual to each subscriber, means for supervising the several central station receiving means from a common point and means for supervising the subscribers receiving means from a common point.

5. In a system of radio broadcast distribution, a district radio distributing station, a plurality of Wire line distributing stations, trunk circuits connecting said district radio distributing station with each of said wire line distributing stations, and trunk lines connecting one of said wire line distributingv stations with each of the other of said wire line distributing stations.

6. In a system of broadcast distribution, a district radio broadcast distributing station, a plurality of groups of subscribers stations, a central station for each group having relay means establishing communication between said district station and its group of subscribers stations said relay means having parts common to the group and parts individual to each subscribers station in the group, means for supervising said common part at each central station from a common point and means for supervising said individual parts at all saidcentral stations from a common point.

7. In a system of broadcast distribution, a plurality of groups of subscribers stations, a central station for each group, radio receiving means at each central station, individual line relays adapted to receive the output of said radio receiving means and relay it into their respective lines, and means controlled from a common point for effecting and testing a supervisory connection with either the input or output side of each of said individual line relays.

8. A central exchange and a plurality of subscribers stations with individual wire circuits interconnecting them, a radio receiving apparatus at the central station, bus wires connected to the output terminal of said receiving apparatus, and an individual line relay device for each line, having input terminals to be connected to said common bus, and output terminals connected to its line, with testing apparatus at said central station, and means to connect said testing apparatus to the input and to the output side of each of said line devices at will.

9. In .a system of broadcast distribution, a telephone central station, a plurality of subscribers stations connected therewith by wired line circuits, radio receiving appara tus at said central station terminal output bus for said receiving apparatus, and individual vacuum tube line relays, each with its input side adapted for connection with said bus, and its output side to its line, together with a wire chiefs position equipped with listening and testing apparatus, and means for connecting the same to either the input or the output side of any of said tubes.

In testimony whereof I hereunto aflix my signature.

EDWARD E. CLEMENT. 

